Electronic organ keying device



April 11, 1967 R. A. BOENNING ELECTRONIC ORGAN 'KEYING DEVICE Filed July.10, 1964 mm cw W mm m m3 wmmamu H $5363 -23 Q vw EEEG w mw.\ w" m mm wmv mm mm m fit M62 m v 9 E s Q\ TTORNEY United States Patent O 3,313,877I 1 ELECTRONIC ORGAN KEYING DEVICE Robert A. Boenning, Timonium, Md.,assignor of fifty. percent to Walter G. Finch, Baltimore, Md.

Filed July 10, 1964, Ser. No. 381,700 8 Claims. (Cl. 84--1.01)

This invention relates generally to music instruments, and moreparticularly it pertains to a keying arrangement for switching on thetone generators of an electronic organ. 7

All electonic organs use some kind of electrical contact in the keyingcircuits to turn on and off the tone generators at the will of theoperator by means of the manual finger keys.

The usual method is-to supply a more or less step variable DC voltage toa control circuit which utilizes a tube or transistor as the actualswitching device. Typically in the case of a transistor, the absence ofa DC. voltage on the base and hence the absence of base current wouldresult in no tone generator output, the presence of DC. voltageresulting in some degree of output.

At present the DC. control voltage is removed or applied by means of aswitch controlled by depressing keys on the manual of the organ, controlvoltage being maximum when the key is fully depressed. However,depending on the tone generator type of circuit, an opposite effect issometimes required, i.e., the control voltage being minimum when the keyis fully depressed. Some circuits may require different polarity ofkeying voltage than others.

Spring wire contacts, sometimes with associated carbon rods are nowused. In the latter case, the output voltage is a minimum when contactis first made and this increases to a maximum at full key depression. Inthis manner, the plop of an initial contact make is reducedconsiderably. Other schemes involve sliding or rolling contacts on aresistance element such as carbon to soften the impact of the keyingvoltage as the key is depressed.

In spite of such features, all the methods have shortcomings because adefinite starting point of contact making is unavoidable and alsobecause of short life of the contacts.

It is an object of this invention, therefore, to provide a key for anelectronic musical instrument which makes no physical contact whenactuated,

Another object of this invention is to provide a key which will actuatea musical instrument tone generator in a smooth manner without thecustomary transients in starting or stopping.

To provide a keying device for electronic organs which can provide akeying voltage of either polarity, is yet another object ofthisinvention.

Still another feature of this invention is to provide a keyingarrangement for the manual of electronic organs which can be smoothedelectrically to furnish keying voltage with any degree of abruptness.

And another object of this invention is to provide a simple,frictionless, inexpensive key for electronic musi cal instruments whichis not subject to contact corrosion or dust; has indefinite life and iseasily and permanently adjusted.

Other objects and attendant advantages of this invention will becomemore readily apparent and understood from the accompanying specificationand drawings in which:

FIG. 1 is a schematic'of an electronic organ keying device incorporatingfeatures of this invention; and

FIG. 2 is a schematic of an electrical system for use with the keyingdevice of FIG. 1.

Referring now to the details of the drawings, an elec- Hce i undersideof the key 12 so as to contact a non-metallic coupling rod 16 which isbiased upwardly by a compression coiled spring 18.

A differential transformer is located so as to receive the rod 16 and besecured to'some immovable portion of the organ. The ferrite core 22 ofthe differential transformer is movable therewithin and is attached tothe rod 16 for actuation thereby as the key 12 is depressed. The spring18 returns the key, rod, and ferrite core when pressure is released.

As shown schematically in FIG. 2, the differential trans- A former 20has three windings 24, 26 and 28. The excitation winding 24 receives anAC. sine Wave potential from a carrier oscillator 40.

The other two or output windings 26 and 28 are identical to each otherand coupled tightly together electromagnetically. They also areconnected in series opposition as shown by the instantaneous polaritydots.

Consequently, when the ferrite core 22 is centered in the windings 24,26, and 28, there are equal voltages induced in the output windings fromthe excitation winding and they buck out to a resultant-zero output.However, should the core 22 be moved, this equality is upset and avoltage appears at terminals 30 and 32.

A rectifier 34, which may be a single diode as shown, is connected tothe output from the terminals 30 and 32 and converts the sine wavevoltage output from transformer 30 to a pulsating DC. The filter RCsmooths this output so that it is a pure DC.

It will be noted that the movement of the ferrite core 22 starts alinear current flow from terminals 30 and 32 from zero to amaximumwithout any abruptness. Consequently, if the rectifier 34 is linear theDC. control voltage at keying terminals 36, 38 will be Withouttransients. This is the desirable keying voltage for electronic keyingof a tone generator 42, connected thereto. By reversing the rectifier34, the other polarity is available where required.

Usually, the position of transformer core 22 is so adjusted with key upthat a small initial output voltage is obtained, not sulficient to keythe tone generator on. This setting can be thus chosen to accept a widevariation in the keying characteristics of the usual tone generat-ors.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A keying arrangement for actuating an electrical element, comprisingtransformer means including a pair of output windings connected inseries opposition and in circuit with said electrical element and aninput winding, said transformer means having a movable core element forinducing voltage from said input winding to said pair of output windingsin accordance with the position of said core element relative to saidpair of output windings, and means for moving said core element to theposition desired including a hinged key element and a rod elementattached to said core element, with said rod element being in operativeengagement with said hinged key for actuation thereby.

2. The keying arrangement as recited in claim 1 wherein said rod elementis biased against said key element.

3. The keying arrangement as recited in claim 1 wherein a nylon pad issecured to the underside of said key element and said rod element ismaintained in contact with said nylon pad.

4. A keying arrangement for actuating the tone generator of an electricorgan, comprising transformer means including -a pair of output windingsconnected in series opposition and in circuit with said tone generatorand an input winding, said transformer means having a movable coreelement for inducing, voltage from said input winding to said pair ofoutput windings in accordance with the position of said core elementrelative to said pair of output windings, and means including a key formoving said core element to the position desired.

5. The keying arrangement as recited in claim 4 wherein when said coreelement is centered between said pair of output windings, the voltagesinduced therein are equal. 1 6. In an electric organ having a tonegenerator and a key for the actuation thereof, means for graduallysupplying voltage' to said tone generator, said means includingatransformer having a pair of output windings connected in seriesopposition and in circuit with said tone generator, an input winding,said transformer having a movable core element for inducing voltage fromsaid input winding to said pair of output windings in accordance withthe position of said core element relative to said pair of outputwindings, and means coupling movement of said key with movement of saidcore element.

7. In the electric organ as recited in claim 6 wherein said meansincludes electrical circuitry for supplying direct current to said tonegenerator from the voltage induced in said pair of output windings.

8. In the electric organ as recited in claim 7 wherein said pair ofoutput windings are substantially balanced so that when core element iscentered therebetween, the induced voltage supplied to said tonegenerator is substantially zero and when said core element is moved, thechange in said induced voltage is substantially linear.

References Cited by the Examiner UNITED STATES PATENTS 2,569,521 10/1951Greaves et al. 84-1.26 3,181,055 4/1965 Bischof 3'23-51 3,185,866 5/1965Harpell 323-51 X 3,217,240 11/1965 Grant et al 336-136 X 3,248,4704/1966 Markowitz et al. 841.01 X 3,255,293 6/1966 Walker 84--1.15 X

ARTHUR GAUSS, Primary Examiner.

D. D. FORRER, Assistant Examiner.

4. A KEYING ARRANGEMENT FOR ACTUATING THE TONE GENERATOR OF AN ELECTRICORGAN, COMPRISING TRANSFORMER MEANS INCLUDING A PAIR OF OUTPUT WINDINGSCONNECTED IN SERIES OPPOSITION AND IN CIRCUIT WITH SAID TONE GENERATORAND AN INPUT WINDING, SAID TRANSFORMER MEANS HAVING A MOVABLE COREELEMENT FOR INDUCING, VOLTAGE FROM SAID INPUT WINDING TO SAID PAIR OFOUTPUT WINDINGS IN ACCORDANCE WITH THE